Objective To measure the frictions between FAS bracket and stainless steel wire under different two conditions, and compare two traditional self- ligating brackets. Methods FAS bracket was a new- style self - ligating bracket with a friction adjusting system（FAS） to adjust the friction as the wires slide in the bracket. Firstly, FAS bracket 20 times of original size was made, then the frictions were measured respectively made by the steel round wires of diameters 8.128 0 mm or the steel square wires in size of 9.144 0 mm×12.700 0 mm. It was divided into two adjusting states, and used the same method to measure DamonⅢ and SPEED bracket in 20 times of original size. Results With the shim entirely drew in, all the frictions of the arch wire had no significant difference with the DamonⅢ. When 8.128 0 mm stainless steel round wire was used, SPEED bracket had no significant difference with FAS. When 9.144 0 mm×12.700 0 mm square wire was used, they had significant difference（P
